The present invention generally relates to vacuum drums, and more specifically to an improved lightweight vacuum drum for use in labeling machines and similar work piece processing equipment.
Generally, labeling machines operate as a means to transport, prepare and apply labels to containers or other work pieces. Labeling machines typically consist of several components including a rotating vacuum drum as a mechanism for picking-up a web of labels, which may be perforated or, alternatively, a label from a cutting wheel or a stack of precut labels, transporting and positioning the label for subsequent application to a container or work piece. Conventional vacuum drums typically incorporate a set of air passages bored in the generally cylindrical side wall thereof to draw labels onto the surface of the side wall in response to negative air pressure therein. The labels are held on the surface by the resulting vacuum while an adhesive is applied or activated, transported to the correct position and orientation with respect to the surface of the workpiece and applied to the work piece by mechanical engagement and reversal of the air flow through the air passages to discharge the discharge the label from the drum surface. An example of a vacuum drum capable of multiple levels of vacuum is taught in U.S. Pat. No. 5,486,253, which is incorporated by reference as if fully set forth herein and which is owned by the assignee hereof.
Labeling speed and efficiency are important considerations in high volume production canning and bottling plants. The maximum speed and performance capabilities of the vacuum drum in labeling systems may be the most significant component in the design of such systems. The higher the speed, the more precise the tolerance needed for balance and control. In addition, a vacuum drum must be very durable in order to endure in the hostile operating environment in which it will likely be operated. In order to satisfy these requirements, conventional vacuum drums have been formed from all-metal components, such as steel, aluminum, titanium, or other alloys. As a result, known vacuum drum arrangements tend to be very heavy, making them difficult to handle during fabrication, assembly, and repair. In fact, some manufacturers construct the drum so as to be disassembled in segments to facilitate handling.
In addition, the machining process used to fabricate the vacuum drum, particularly forming the air passages in the cylindrical surface, requires expensive machine tools. However, other processes are also used. In addition to materials expense, the overall machining process required for steel, aluminum, titanium, and alloy vacuum drums is very time consuming and labor intensive.
As a result, a need exists for an easily machinable, lightweight vacuum drum which does not otherwise sacrifice optimal performance and durability characteristics.
The present invention provides a lightweight vacuum drum for picking-up, holding, transporting and positioning label segments for application to a work piece. In a labeling machine utilizing the present invention, the main drum comprises a cylindrical drum, core a support flange affixed to the bottom of the core and a top ring affixed to the top of the core. The core is formed from a polymeric casting, investment casting, or extrusion.
The main drum core includes a generally cylindrical wall having a plurality of vacuum ports formed therein, and a first set of air passages positioned to be in fluid communication with the plurality of vacuum ports. The support flange is fastened to the bottom end of the main drum core cylinder, and includes a second set of air passages formed therein and aligned to overlap the first set of air passages in the cylindrical wall of the main drum core. The second set of air passages are arranged to provide a continuous path for withdrawing air therefrom to form a vacuum thereat. Forming the main drum core from a polymeric material allows more flexibility in design, placement, and orientation of the ports over conventional metal drums. A hub connector is fastened to the support flange for coupling the vacuum drum to a drive shaft located in the labeling machine.
In accordance with one embodiment of the present invention, the main drum core is formed from a nylon based cylindrical wall casting or investment casting coupled to a nylon based bottom ring casting. The support flange and hub connector are formed from either aluminum or a nylon based material. The vacuum drum is connected to an external air pump which draws a vacuum within the drum so that the ports operate to pick-up and hold a label to the outer surface of the drum. Alternatively, the pump produces positive air pressure through the ports to discharge the label from the outer surface to assist in placement of the label on a container or work piece. The vacuum ports can be coupled to an external vacuum control which can vary vacuum or air pressure to meet a desired purpose or application.
In accordance with the present invention, the cylindrical walls of the drum core are flexible. The amount of flexure can be controlled by the composition and malleability of the polymeric material used, the positive and negative air pressure invoked, and by mechanical means to apply force to the rotating cylindrical wall.
These and other advantages of the present invention will become apparent to one of ordinary skill in the air in light of the following description and attached drawings.